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re: Code Coverage is Useless VIEW POST


I stopped reading somewhere in the middle. Test coverage for every project should be set to 100%. Test coverage doesn't mean you will not have bugs but it is proven that projects with higher test coverage have significantly less bugs. 100% is a must and if you feel like some file is not worth testing (although never seen such) then exclude it from the coverage. The cost of bugs are several times higher then the cost of writing tests hence write tests, don't be that lazy know it all who thinks his code is the best and it will not change and why and what not..excuses are the meantime I am going forward with full coverage and almost no bugs :) ..TDD was invented for a reason you know :)


As highlighted in the article, if you're using TDD, I'd almost argue setting coverage is redundant. It's nice as an enforcement mechanism, but TDD is going to have you at or near 100% coverage anyway.

The moral here is that while you may be leveraging TDD like a rockstar, you may have other peers on your project who are not and will do silly things just to hit the 100% goal.

I personally feel coverage works best as a metric. It should stay consistent or be on the upswing. A little dip here and there is perfectly acceptable, but a consistent drop would warrant some investigation.


Agree. Decide what should you test, and then ensure 100% coverage.
Ask why automatic tests exist. Testing all edge cases within the complex logic in your head is impossible. Humans have scarce of cognitive capacity for it. So automatic tests are must have there.

Although testing if React component is properly rendered is something what usually doesn't bring any value and cost time for coding and maintenance so probably you don't want to do this.


I agree. Having ten files with full coverage is better than all files with 80% coverage. This is because having full coverage for ten files allows applying mutation testing against those ten files. Once you get the tests good enough that mutation testing cannot find missing tests, then you can be pretty sure that the tests really test the full implementation insteard of simply run every line of code once and cover random part of the actual implementation.

I mean, 100% coverage is not bad thing itself but that does not mean you have good tests in reality.

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